The present invention relates to a method of cutting a block of insulation material to form an insulation piece for a pipe elbow.
It is commonly required to insulate pipes both when the pipes are hotter than the environment and when the pipes are colder than the environment. Larger size pipes such as those having a diameter of the order of 3 inches or greater are usually insulated by attaching half cylindrical portions of solid insulation material which are engaged onto the pipe from opposite sides and which are joined at a central plane. It is also necessary to effect insulation of the pipe at elbows which may be 90xc2x0 or 45xc2x0 elbows. At the present time elbows are available but only fabricated from pieces of insulation material which are glued together to form the required structure. One example is shown in U.S. Pat. No. 4,363,681 (Williams) issued December 1982. This patent refers back to an ASTM publication xe2x80x9cPrefabrication and Field Fabrication of Thermal Insulation Fitting Coversxe2x80x9d Page 140-1969 which discloses a ten piece assembly in which the insulation pieces are manually cut, pitted and interconnected. This is of course a complex unskilled operation and is thus expensive.
Yet further the fabrication of the elbows from separate pieces requires that the elbows be joined by glue lines and these glue lines can fracture under the significant temperature changes involved and can act as a conduit for heat transfer thus interfering with the insulation effect.
Up till now, therefore, no insulation elbow has been available which is cut from a solid insulation material in an integral piece, particularly in larger diameters where the external diameter of the insulation piece at the elbow is of the order of 9 inches.
It is one object of the invention therefore to provide an improved method of forming an insulation piece for a pipe elbow and a piece so formed.
According to one aspect of the invention there is provided a method of forming an insulation piece for joining with a similar piece to surround a pipe elbow, the method comprising:
providing an outer arcuate blade portion extending around an angle of greater than 180 degrees and cut from a metal plate so as to define a depth between two edges of the blade portion equal to the plate thickness and a thickness between two side surfaces formed by two cut lines in the metal plate;
providing an inner arcuate blade portion extending around an angle of greater than 180 degrees and cut from a metal plate so as to define a depth between two edges of the blade portion equal to the plate thickness and a thickness between two side surfaces formed by two cut lines in the metal plate;
the outer arcuate blade portion having a diameter greater than the inner arcuate blade portion;
each of the arcuate blade portions being integrally formed with a holder portion cut from the plate which connects ends of the arcuate blade portion to maintain the blade portion rigid;
mounting the holder portions of both of the ring members on a holder so as to rigidly carry the arcuate blade portions substantially in a common plane and centered about a common center;
the holder being arranged to engage the holder portions of the ring members leaving an angle of the arcuate blade portions greater than 180 degrees exposed and open at a top portion thereof;
providing a table surface in a table plane at right angles to the plane and containing the center;
providing on one of the edges of each of the blade portions of the ring members a plurality of sharpened, hardened cutting teeth members;
oscillating the holder and the arcuate blade portions thereon about an axis at right angles to the common plane and passing through the center such that the blade portions of the ring members are exposed above the table plane and reciprocate about the axis in a cutting action;
locating a block of insulating material on the table so that one surface of the block moves across the table plane through the common cutting plane such that the outer blade portion cuts a generally circular outer surface of the insulation piece and the inner blade portion cuts a generally circular inner surface of the insulation piece;
and guiding the movement of the block in a part circular path about a guide axis at right angles to the table plane with the guide axis located so that the blade portions cut through the block each along a part circular line at a radius of curvature from the guide axis arranged to match a respective radius of curvature of the pipe elbow.
Preferably the cutting teeth members are carbide tips having a width greater than the thickness of the ring member.
In one possible arrangement, the holder portion of each arcuate blade portion is arcuate so as to define therewith an annular blade member and wherein the holder defines a pair of arcuate slots extending over an angle of at least 120 degrees each receiving and locating the arcuate holder portion of a respective one of the blade members. In this arrangement, the holder preferably comprises a back plate, and a pair of mounting plate portions mounted on the back plate and defining the slots therebetween. Yet further, the holder preferably includes a front clamping plate attached to the back plate and clamping the ring member therebetween.
In an alternative arrangement, the holder portion of each blade portion comprises a plate portion cut from the same plate in an integral structure with the blade portion but wider than the relatively thin blade portion so as to provide rigidity to the blade portion during cutting and arranged for clamping to a back plate of the holder.
In another alternative, the inner blade portion is cut from a thinner plate than the outer blade portion.
In a yet further alternative, the holder portion of each of the blade portions forms a common plate member for attachment to the holder.
Preferably the outer blade portion has a diameter greater than 9 inches and more preferably 12 inches.
The invention also provides as a second aspect an insulation piece for joining with a similar piece to surround a pipe elbow when formed by the method as defined above.
According to a third aspect of the invention there is provided an insulation piece for joining with a similar piece to surround a pipe elbow comprising:
a block of insulating material;
the block having a joining plane for attachment to the similar piece;
the block having an outer surface defining a circular arch relative to the joining plane and cut by an arcuate blade;
the block having an inner surface defining a circular arch relative to the joining plane and cut by an arcuate blade;
the outer and inner surfaces being curved about a common axis at right angles to the common plane arranged to match a respective radius of curvature of the pipe elbow;
the circular arch of the outer surface having a diameter greater than 9 inches.